Interference prevention for radio operated relays



Dec. 18, 1934. c 5 R K 1,984,379

INTERFERENCE PREVENTION FOR RADIO OPERATED RELAYS Filed an 9; 1951 Appms ii yi leceirer{ dv'lds' BJI-ick Patented Dec. 18, 1934 UNITED STATES PATENT OFFICE Carlos B. Mirick.

Washington. D. G.-

Applicatlon Jilly 9, 1931, Serial No. 549,728

6 Claims.

(Granted under the act 01 March 3, 1883, as amended April 30, 1928; 370 (1. G 757] My invention relates to improvements in the method of and means for guarding radio operated relays against interference. in which a plurality of relays, each responding to a different frequency, must operate simultaneously.

MyPatent No. 1,597,416 of August 24, 1926 shows that a system-of selection of radio controlled relays can be devised depending upon the selective tuning of mechanically and electrically I tuned-relays in the output of a receiver.- It further-shows' that such selected relays can be operated simultaneously aswellas individually. It is uponflthis principle that the present invention isbased.-

The objects of my invention are, first; to provide amethod oi guarding radio operated relays against interference.

Second, to provide means for guarding radio operated relays against. interference.

1 practice my method and attain these objects with the apparatus. illustrated in the accompanying-drawing which is a schematic diagram of the apparatus.

:Retenence numbers 1, 2 and 3 are selective, mechanically and electrically tuned relays as described in Patent no. 1,597,416. Reference numbers), 11 and .12 are electric relays. thenoutput-of a radio receiver. iii-and mare control circuits.- is is a source of electric potentialior control circuits-15' and 16.

. The operation of'myinvention isiasi'oliows:

transmittm is employed that has associated therewith a modulator comprising a plurality of audio frequency oscillators or vibrators that are tuned to frequencies slightly separated, such as cycles. These vibrators are so arranged that the transmitter can be simultaneously modulated by one or more of them, as desired. The receiver has a corresponding number of tuned relays which are responsive respectively to the corresponding frequencies of the vibrators. It is evident that by modulating the transmitter by one or more of the vibrators, the corresponding tuned relays associated with the receiver can be caused to operate. Thus, in the apparatus as shown in the drawing, the three relays 10, 11 and 12 can be selected singly or in pairs by operating the distant radio transmitter. Tuned relays 11 and 12 operate control circuits while tuned relay 10 is connected as a guard relay which must be closed simultaneously with 11 and 12 before potential is supplied to the control circuits which it is desired to operate.

The purpose of this arrangement is to make it necessary to use two frequencies of modulation to operate any control circuit. A single pitch of modulation can be readily identified and interiered with. But two simultaneous tones, particu larly if they are in dissonance, are very dimcult to identify with the human earand are correspondingly hard to imitate. It is to be understood that more than two such relays may be associated together to cause the control circuits to be closed, thereby limiting to a greater degree the exact conditions necessary for the control circuits to become complete and thereby obtaining greater security from interference. The im-- portance of this feature'increaseswhen such interference is intentional.

It is to be further understood that the so-called output circuits may be used tooperate controls or to set up combinations-in. secondary relays in some one of the many systems of this kind to further protect the selection against interference.

My invention is :a. protection. against-interference to relays operated. by remote. radio transmis alon so connected that a-pluraiity-oi frequencies of modulation must be employed simultaneously or a plurality of locally generated frequencies must be produced by local heterodyne as described in-my co-pending application 5493729 at July 9,

in the above descript'sonzofwmy invention it has been assumed that-the radio; re'ceiverconnected to leads '13 was-of the'typeadapted to-derive. from a modulated carrier frequency the -original selective frequencies used to-.-modulate the;.carrier at the transmitter. When a plurality of unmodulated radio frequency signals are used to control the energization of certain of the relays 10, 11 and 12, it is necessary that these signals be reduced in frequency by the proper amount so that they can be used to operate the relays. This can be accomplished by beating the incoming radio frequencies with a locally generated frequency and separating the beat components corresponding to the difierent received frequencies from the mingled frequencies by detection. Numerous types of so called heterodyne receivers are adapted to be used with my invention, but for the purpose of illustration a receiver of a type disclosed in my application Serial No. 549,729 filed July 9, 1931, is shown connected by means of a switch 1'? to the leads 13 in lieu of a conventional receiver normally connected to the leads 13. This receiver consists of a crystal controlled or other type of local oscillator 18 coupled to an antenna excited detector 19, the heterodyne output of which is used to control the energization of the tuned relays.

The herein described invention may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalties thereon or therefor.

What 1 ms: .h i.

1. In a system for gjuarding "radiooperatefd relays against interference, when a wave of radio frequency modulated at a plurality of frequencies has been transmitted, received and detected; a first group of tuned electrical systems operable each at a separate predetermined frequency and functioning simultaneously to supply potential to at a separate predetermined frequency, each of said other groups functioning simultaneously with said first group to operate a control circuit, and means for impressing" said: modulation. as. quencies simultaneously upon all of said groups of tuned electrical systems. -2. In a system-fongnarding radio operated relays against interference, when a wave of radio frequency modulated at a plurality of frequencies has been transmi-tted,- received and detected; a first tuned electrical system operable at a-predetermined .frequency and functioning to supply electrical potential to aplurality of control circuits, a. pluralityof other tuned electrical systems each-operable at a separate predetermined-frequency each functioning simultaneouslywith said first tuned electrical system to operate a:control circuit, :an d means for impressing said modula: tion frequencies simultaneously upon alleofsaid tuned electrical-systems, 1 -I 3.- Ina system for: guarding'radio operated ire-- lays against interference when a plurality of-undamped :waves each at a separate radio frequency have been transmittedreceived, combined-with'a locally generated-heterodyne and detected, a first group. of tuned-z electrical systems operable each at a separate predetermined frequency and'funcs tioning simultaneouslytc supplypotential to a plurality of controlcircuits, a; pluraiity-'o'f=other groups. of tuned electrical systen'is eacli-iloperableat a: separate J'pr'edetermined vfrequency, each of:

said other groups functioning simultaneously wit-'11" said first group to zoperatfiaf'control-circuit; and

'ia-system for guarding radio-operate'd lays against interference when a plurality of undamped waves each at a separate radio frequency have been transmitted, received, combined with a locally generated heterodyne and detected, a first tuned electrical system operable at a predetermined frequency and functioning to v supp y electrical potential to apluraut'y of'control circuits, a plurality of other tuned electrical systems each operable at a separate predetermined frequncy each functioning simultaneously with said first tuned electricalsystem to operate a control circuit, and means for impressing said beat fre- 4 quencies simultaneously upon all of said tuned a plurality of control circuits, a-plurality-of'otlii" groups of tuned electrical systems each operable electrical systems.

5, A rnethod of avoiding radio interference of radio controlled mobile objects comprising; genera'ting a wave of radio frequency, simultaneously modulatingsaidwaye, at a preselected plurality of effecting predetermined control operations each in response to the concurrent effect of a different plurality-of said preselected separate audio frequencies. 3

6. A radiodynamic system for selectively actuating any one-of a plurality of control devices by theconjoint; action of a'plurality of waves of difierentfrequencies and guarding against ;the operation of any one of said control devices by the-reception of asingle wave of spurious frequency, comprising a first group of tuned electrical system$;.;.0perab1e each at a separate predetermined; frequencyv andfunctioning to simultaneously supply potential to a plurality of controlcir cuits, a plurality of other. groups of tuned electrical systems operable each at a separate .predeter.-.

mined frequency different from the frequencies foriactuating saidfirst group of tuned electrical systems, eachmf said other groups-functioning simultaneously with said first group to complete control circuits and effectthe actuation of control devices :only when said groups of tuned electrical systems are energized by a plurality of waves .of

different-frequency at least one of which is the resonantfrequen'cy of one of the tuned electrical systems "of the firsttsaid groupxand at least-am other of which the-resonant frequencyof onepf tlsieztuiiedv electrical systems ofoneof said'groups. other-than? said" first group, and means for irn'-" pressing all ofsaid frequencies simultaneously: upon all of said grou'psof tuned'electrical systems.

CARLOIS' B.-1VIIRIQK. 

